8345975

Automatic Exposure Estimation for Hdr Images Based on Image Statistics

PublishedJanuary 1, 2013
Assigneenot available in USPTO data we have
Technical Abstract

Patent Claims
15 claims

Legal claims defining the scope of protection, as filed with the USPTO.

1

1. A method of segmenting regions of an image comprising the steps of: determining a number of partitions based on a range of a histogram of the image; defining regions by the partitions; estimating a centroid of each region; assigning pixel data to the estimated centroids by assigning each pixel data point to its nearest centroid to form a plurality of clusters; estimating new centroids by taking the mean of each cluster; and, determining anchor points based on the new centroids.

2

2. The method of claim 1 wherein the centroid is determined by K-means clustering applied in a logarithmic luminance domain.

3

3. The method of claim 2 wherein anchor points are based on a half distance between adjacent centroids.

4

4. The method of claim 3 further comprising the step of computing a weight of each pixel within each region.

5

5. The method of claim 4 further comprising tone mapping the image based on the pixel weighting.

6

6. A method of segmenting regions of an image comprising the steps of: determining a number of partitions based on a range of an image histogram in a logarithmic luminance domain; defining regions by the partitions; calculating a mean value of each region by K-means clustering wherein the clustering is initialized, data is assigned and centroids are updated; determining anchor points based on the centroids; and, computing a weight of each pixel based on the anchor points.

7

7. The method of claim 6 wherein the cluster is initialized by one of a random seed method or a random partition method.

8

8. The method of claim 7 wherein the centroids are updated by an iterative process.

9

9. The method of claim 6 wherein regions are permitted to overlap.

10

10. The method of claim 6 further comprising the step of normalizing the weights.

11

11. The method of claim 6 further comprising the step of binarizing the weights.

12

12. A method of segmenting regions of an image comprising the steps of: designing an energy function based upon a probability of anchor points in an image histogram; iteratively differentiating the energy function using a chain rule to determine the anchor points; and, computing a weight of each pixel in the image based on the anchor points.

13

13. The method of claim 12 wherein the energy function is expressed as: J = ∑ i ⁢ p L i ⁡ [ ( 1 - ⅇ N 1 ) × ⅇ N 1 ⅇ N 1 + ⅇ N 2 + ⁢ … ⁢ + ⅇ N k + ( 1 - ⅇ N 2 ) × ⅇ N 2 ⅇ N 1 + ⅇ N 2 + ⁢ … ⁢ + ⅇ N k + ⁢ … ⁢ + ⁢ ( 1 - ⅇ N k ) × ⅇ N k ⅇ N 1 + ⅇ N 2 + ⁢ … ⁢ + ⅇ N k ] where ⅇ N j = ⅇ - [ S ⁡ ( L 1 A j ) - 0.5 ] 2 σ 2 ⁢ (j=1, 2, . . . , k) and where i is an index of bins in the histogram, L i is a corresponding luminance value, P L is a probability of L i , {A j } are the anchor points, σ is a constant, and S(•) is a saturation function, defined by S ⁡ ( x ) = { 1 x > 1 x 1 / γ otherwise .

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14. The method of claim 13 wherein e N j is a Gaussian curve which defines a measurement for exposure.

15

15. The method of claim 14 further comprising a gradient descent method applied at the differentiating step.

Patent Metadata

Filing Date

Unknown

Publication Date

January 1, 2013

Inventors

Zhe Wang
Jiefu Zhai
Joan Llach

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Cite as: Patentable. “AUTOMATIC EXPOSURE ESTIMATION FOR HDR IMAGES BASED ON IMAGE STATISTICS” (8345975). https://patentable.app/patents/8345975

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